If you are working, try to negotiate the offer up. You have nothing to lose. You have a job and a salary, so if they say no, then you still have your job to fall back on. I think the main factor to consider is salary, because it affects all of your other life activities. If it's unacceptable and they're not willing to make it acceptable, then walk- they're just not that into you.

You need to weigh how much you like the position and company versus how much you like money. If money is more important to you, this might not be an ideal opportunity for you and you should keep looking. Examine the potential for future advancement at the company as well, because it could be a position that starts low but gives you advancement opportunities quickly.

Don't rule out negotiation either-- you can tell them about the research you have done, about your current salary, and that you feel that you are worth more than the offer you received. Back it up with accomplishments, and they just might come back with another offer. Call their bluff-- the worst that could happen is they refuse to negotiate, in which case you’ve lost nothing.